1. Field of the Invention
The present invention relates generally to methods and systems for measuring wear on material surfaces. The present invention relates more specifically to methods and systems for measuring the wear on a surface utilizing contact autoradiographs of residual radiation established by surface layer activation.
2. Description of the Related Art
Efforts have been made in the past to provide systems and methods for tracking, measuring, and monitoring the degree of wear on a variety of material surfaces. Of particular interest is the degree of wear that occurs over time on surfaces that, by operation of the machinery they are associated with, encounter abrasive surfaces or other metallic surfaces with the result that over time a significant amount of wear can occur. Many such surfaces can be found on critical engine components and other elements of vehicle systems that repetitively, or periodically, move against one another in a manner that produces wear over time. Knowing the degree and pattern of wear in components like these can be critical to safety and maintenance protocols associated with the machinery and equipment the components serve. Such testing further promotes and facilitates the development of improved designs and manufacturing techniques for these mechanical structures.
A number of efforts to determine the degree of wear on a surface involve placing or depositing some measurable characteristic onto the surface that will gradually be worn away as the surface itself is worn away. In some of these systems, this deposition process involves the placement of an additional over-layer on the surface and other times it involves providing some measurable characteristic to a surface layer (or layers) of the material itself. One obvious drawback to the use of the former approach (depositing an additional layer) is the resultant change in the character of the surface over time as the deposition layer is worn away. A further drawback is the fact that this additional layer will likely change the wear characteristics of the material. Preference is given therefore to techniques that utilize the actual material that the surface is made up of already, and that instill some characteristic in the upper layers of the material which can be monitored and measured over time.
The simplest example of such a wear monitoring system would involve a material that can be modified in some visual form on the upper layer or layers of its surface. Often this takes the form of creating physical patterns in the surface layers of the material when it is manufactured such that over time the patterns are changed or become visibly exposed as the wear on the surface occurs. This procedure, however, also suffers from the fact that the surface thereby changes physical appearance and therefore its physical characteristics, which could ultimately have an effect on the manner in which the surface interacts with other surfaces that it comes in contact with.
It would therefore be preferable if a wear monitoring system did not result in a physically changed surface over time and maintained the physical surface characteristics (with the exception, of course, of the wear that occurs) and therefore does not affect the manner in which the part or component functions (again, at least not beyond the extent to which the wear itself affects the functionality of the component).
The process of instilling a material with a characteristic that resides only in a surface layer can take a number of different approaches or forms. It is possible for example to provide a color dye to a material, with coloration variation according to a depth away from the surface into the material. Some such components may for example incorporate red dyes deep within the material, with green or blue dyes residing within the upper surface layers of the material, or more simply the density of the dye may vary according to depth. As the surface is worn away, areas beneath the surface are exposed and, upon visual inspection, differences can be determined in the degree of wear over different parts of the component. Such visually inspectable systems have drawbacks in that the degree of wear generally has to be significant in order for distinctions to be made between the upper layers and lower layers of the material. In addition, many materials are simply not receptive of dyes; at least not to the extent that visual inspection might discern quantifiable information.
Autoradiography is a process whereby the radioactive properties of a material are mapped by imaging the surface of the material (typically with photographic or x-ray film, although any two-dimensional detector array will do) and measuring the radiation generated by each particular surface area component. Autoradiography refers to the process of measuring the radiation generated by the object itself (as opposed to reflected or absorbed radiation measurements) and is generally carried out in a manner that creates an image of the radiation source whereby the radiation intensity varies in different portions across the view being measured. Such systems are used, for example, to locate radiation leaks in closed systems, and other fields where low level radiation is generated by an object in a manner that requires monitoring or tracking.